The invention relates generally to the field of systems which monitor and/or control multiple cylinder engine performance.
It is known that detection of engine knock is desirable such that engine operating parameters can be adjusted to avoid such a condition. Generally, knock detection is accomplished in accordance with the output of one or more special sensors designed specifically to detect engine knock. Some of these sensors detect knock by virtue of detecting audible knock sounds or vibrations produced by the engine in a single sensor. Other knock sensors detect abnormal engine cylinder pressure variations in each cylinder. Providing one or more additional knock sensors to an engine system results in increasing the complexity and cost of such engine monitoring/control systems.
Some prior systems have proposed that a specific type of engine cylinder failure can be detected by detailed analysis of the instantaneous engine crankshaft speed signal produced in response to each cylinder's power cycle. In such systems, apparently a certain portion of the engine crankshaft speed signal is monitored during an associated power cycle of each cylinder to create an instantaneous cylinder associated speed vector signal By comparing the variations produced in the speed vector signals to some type of reference criteria an indication of a single fault, such as engine misfire, can be achieved. However, these systems do not discuss how it is possible to use such a system to determine engine knock or any other type of engine cylinder fault or undesired engine cylinder performance.
One prior engine control system recognized that it is desirable to adjust fuel to individual engine cylinders so as to obtain power balancing between these cylinders such that each cylinder contributes approximately the same power with respect to driving the engine crankshaft. In this system, the engine crankshaft speed was measured at a certain position of each cylinder power cycle during an engine idle speed mode. The measured crankshaft speed was then compared with the known desired engine idle speed, and fuel to each of the cylinders was adjusted in an attempt to have each engine cylinder achieve the same desired idle speed crankshaft speed at the power cycle position at which the crankshaft speed was measured. Such a system which uses a known desired engine speed would apparently not be usable at conditions other than the engine idle speed mode where the desired crankshaft speed was known. Also, in such a system the balancing of individual cylinder power might run contrary to other engine performance criteria, such as maintaining the average amount of fuel consumed at a predetermined level to reduce engine pollutants in the exhaust. Thus, the functions of maintaining engine exhaust pollutants below a maximum permissible level and implementing balanced engine cylinder power might not be readily achieved in the prior system.